1. Technical Field
The present invention relates to a method for manufacturing a semiconductor device using a process for forming a tungsten layer in a hole formed in an insulating layer.
2. Related Art
A contact plug is usually used to connect a transistor to an upper interconnect layer or to connect an interconnect layer to another interconnect layer. A contact plug is formed by forming a tungsten layer in a hole formed in an insulating interlayer, for example, as stated in Japanese Laid-open patent publication No. 11-87268, Japanese Laid-open patent publication No. 2007-9298, Japanese Patent Application National Publication (Laid-Open) No. 2001-525491, and U.S. Pat. No. 6,309,966.
Among Patent Documents, Japanese Laid-open patent publication No. 11-87268 discloses that in order to selectively grow a tungsten layer in a hole, a first tungsten layer is formed at a temperature of 200° C. to 260° C., and then a second tungsten layer is formed at a temperature of 280° C. to 340° C. According to Japanese Laid-open patent publication No. 11-87268, if the temperature is higher than the above temperature, resistance becomes larger, and the selective growth is impossible.
Japanese Patent Application National Publication (Laid-Open) No. 2001-525491 discloses that when a tungsten layer is formed by a nucleation step and a bulk deposition step, a pressure increasing step is performed between the nucleation step and the bulk deposition step. In the pressure increasing step, a tungsten-containing source is not contained in process gas. In Japanese Patent Application National Publication (Laid-Open) No. 2001-525491, a substrate temperature is set to 325° C. to 450° C.